Method of forming an aluminum bronze article



United States Patent 3,505,104 METHOD OF FORMING AN ALUMINUM BRONZE ARTICLE Quentin F. Ingerson, Milwaukee, Wis., assiguor to Ampco Metal, Inc., Milwaukee, Wis., a corporation of Wisconsin N0 Drawing. Filed Oct. 27, 1966, Ser. No. 589,802

Int. Cl. C23c l/00 US. Cl. 117131 Claims ABSTRACT OF THE DISCLOSURE An aluminum bronze article having improved wear resistance and surface hardness. The article comprises an aluminum bronze core having an aluminum content in the range of 5 to 13% and aluminum is diffused into the outer surface of the core and alloys with the existing metallographic phases of the core to provide a hard wear resistant outer layer having an increased aluminum content generally in the range of 13 to 16%.

This invention relates to a wear resistant aluminum bronze article and to a method of making the same.

In many instances aluminum bronze alloys containing from 5 to 13% aluminum have the physical properties for a specific application, yet lack the required wear resistance or surface hardness. To obtain increased wear resistance and surface hardness, it is normally necessary to modify the alloy composition by increasing the aluminum content to a value in the range of 13 to 16%, a marked increase in Wear resistance is obtained, yet the increased aluminum content results in a pronounced decrease in forming and machining properties. For example, by increasing the aluminum content of the aluminum bronze alloy, the tensile strength, hardness and wear resistance are increased, but with each phase change the alloy becomes increasingly more brittle and difficult to form and machine.

The present invention is directed to an aluminum bronze article having improved wear resistance and surface hardness. The article comprises a central ductile core of an aluminum bronze alloy having an all alpha, alpha and beta, or all beta metallographic structure, depending on the aluminum content, and a hard, wear resistant outer surface layer having a beta, beta plus gamma-two, or all gamma-two metallographic structure.

The basic aluminum bronze core material, having an aluminum content generally in the range of 5 to 13%, can be readily formed and machined. After forming, the article is subjected to a surface hardening treatment in which aluminum is diffused into the outer surface of the article to provide a hard, wear resistant outer surface layer having an aluminum content in the range generally of 13 to 16%. More specifically, the surface hardening treatment consists of heating the aluminum bronze article to a temperature in the range of 1300 to 1700 F. in the presence of powdered aluminum and a halide in a closed chamber. The article is maintained in the chamber for a period of time sufiicient to diffuse the aluminum into the outer surface of the aluminum bronze article to obtain the hardness and depth of penetration desired.

The article is then cooled in the chamber, and as the slowness of cooling may tend to convert the beta phase of the core alloy to the eutectoid, the article is normally reheated to a temperature of about 1100 F. and maintained at this temperature for a period of about 1 to 3 hours and quickly cooled to room temperature.

The article of the invention has a relatively ductile core with a hard wear-resistant surface layer. The basic aluminum bronze core material can be formed to its final shape and then treated to diffuse the aluminum into the 3,505,104 Patented Apr. 7, 1970 surface and provide the hard and wear resistant surface ayer.

The aluminum bronze core material to be treated can be any conventional aluminum bronze alloy containing generally from 5 to 13% aluminum. The aluminum bronze can contain a wide variety of alloying elements such as iron, nickel, manganese, tin, zinc, silver, cobalt, chromium, vanadium, and the like. Examples of aluminum bronze alloy compositions which can be treated in accordance with the invention are as follows in weight percent:

Alloy Composition Si 1-5 Cu Balance Balance Balance Balance Balance Balance Specific examples of aluminum bronze alloys falling within the above ranges are as follows in weight percent:

Alloy Composition The core material generally has an all alpha, alpha and beta, or all beta metallographic structure as alloys of this type can be readily formed and machined, while the other wear resistant surface layer will generally contain from 13 to 16% aluminum and consist of an all beta, beta plus gamma-two or all gamma-two metallographic structure.

The aluminum concentration of the surface layer will decrease progressively from the outer extremity of the article inwardly toward the core. The depth of penetration of the aluminum which is diffused into the core material depends on the time of treatment. The depth of penetration can be up to 0.10 inch and generally the hardened surface layer will have a depth in the range of .010 to .025 inch in the finished article.

The aluminum is diffused into the outer layer of the aluminum bronze core material by a conventional diffusion process commonly referred to as a Calorizing process. According to this process, the core material is placed in a closed chamber which is packed with powdered aluminum, an ammonium halide or a hydrogen halide and a refractory material such as aluminum oxide, kaolin, or the like. The materials are heated generally to a temperature in the range of 1300 to 17 00 F. and preferably 1500 to 1650 F. and held at this temperature for a period of about 4 to 8 hours depending on the hardness and penetration desired. At this temperature the aluminum is diffused into the surface of the aluminum bronze core material to provide a surface layer having an increased aluminum content, generally in the range of 13 to 16%.

The aluminum bronze core material having an aluminum content in the range of 6 to 13% will generally have a hardness in the range of 55 Rockwell B to 30 Rockwell C, while the hardened outer surface layer will generall have a hardness in the range of Rockwell B to 60 Rockwell C.

Following the heating period the article is cooled in the closed diffusion chamber to room temperature. During this slow cooling cycle, the beta phase in the aluminum bronze core material, if the core is a duplex alloy, may be converted to the eutectoid which will cause brittleness in the alloy. To eliminate the eutectoid phase the article is reheated to a temperature generally in the range of 1100 to 1250 F. and maintained at this temperature for a period of l to 3 hours. Following this heat treatment, the article is rapidly cooled to a temperature under 600 F. at a rate faster than 80 F. per minute. This cooling rate can be conveniently obtained by fan cooling.

The article produced by the invention can be used in any application where surface hardness or wear resistance is a requirement. For example, the article can be used as a die material requiring a substantial amount of machining. The material can also be used for shafts or bearing members which are prone to galling, or for gear parts such as wrench jaws on safety tools or gear teeth on gear trains.

The following examples illustrate specific applications of the invention.

EXAMPLE NO. 1

An aluminum bronze test specimen 1%" x Vs" x and consisting of 6.7% aluminum, 2.3% iron, 0.2% tin and the balance copper was subjected to the surface hardening treatment in a chamber containing powdered aluminum, aluminum oxide and ammonium iodide. The specimen was heated to a temperature of 1600 F. and maintained at this temperature for a period of 8 hours. After cooling to room temperature, the hardness of the core material was 65 Rockwell B, while the hardness of the outer surface layer was 85 Rockwell B.

The specimen was then reheated to a temperature of 1250 F. maintained at this temperature for a period of 2 hours and subsequently water quenched. The hardness of the core material after heat treatment was 5 8 Rockwell B and the hardness of the outer surface layer was 98 Rockwell B.

EXAMPLE NO. 2

A 1%" x /8" x aluminum bronze test specimen having a composition consisting of 10.3% aluminum, 3.5% iron and the balance copper was subjected to a surface hardening treatment similar to thasdescribed with respect to Example No. 1.

After the surface treatment the article had a hardness of 36 Rockwell C from the outer surface, a hardness of 32 Rockwell C A!" from the surface and a hardness of 25 Rockwell C A" from the surface.

The core material had a metallographic structure consisting of a matrix of beta containing particles of intermetallic compound, while the diffused outer surface layer had a metallographic structure consisting of beta, gammatwo and intermetallic particles.

Various modes of carrying out the invention are contemplated as'being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. A method of forming an aluminum bronze article having improved wear resistance and surface hardness comprising the steps of forming an aluminum bronze alloy containing from 5 to 13% by weight of aluminum into substantially final shape, heating the alloy to a temperature in the range of 1300 F. to 1700 F., and diifusing aluminum into the outer surface of the heated alloy to an extent such that the aluminum alloys with the original metallographic phase of said aluminum bronze alloy to change said original metallographic phase and provide an outer hardened aluminum bronze surface layer having an aluminum content generally in the range of 13 to 16% by weight, said outer surface layer having substantially increased hardness and wear resistance as compared to said alloy.

2. The method of claim 1, and including the steps of reheating the alloy to a temperature suificiently high to convert any eutectoid phase in the alloy to beta phase,

and thereafter rapidly cooling the alloy to room temperature at a rate sufficiently fast to prevent transformation of the beta phase to eutectoid.

3. The method of claim 2, in which the alloy is reheated to a temperature in the range of 1100 to 1250 F., and maintained at said temperature for a period of 1 and 3 hours, and the alloy is rapidly cooled to a temperature below 600 F. at a rate faster than F. per minute.

4. The method of claim 1, in which the alloy has a metallographic structure selected from the group consisting of all alpha, alpha plus beta and all beta, and said outer layer has a metallographic structure selected from the group consisting of all beta, beta plus gamma-two and all gamma-two.

5. The method of claim 1, in which the step of diffusing aluminum into the outer surface of the alloy comprises heating the alloy in a closed chamber in the presence of finely divided aluminum and a halide, maintaining said alloy in said chamber for a period of time suflicient to cause the aluminum to penetrate into said alloy to a depth up to 0.010 inch, and thereafter slowly cooling the alloy to room temperature.

References Cited UNITED STATES PATENTS 2,870,051 l/l959 Klement 148-13 2,982,016 5/1961 Drummond l17107.2 X 3,061,462 10/1962 Acton l17-l07.2 X 3,404,998 10/1968 Pesetsky 14813 X 3,375,129 3/1968 Carley 117l07.2

HYLAND BIZOT, Primary Examiner U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 505 104 Dated April 7, 1970 Inventor(s) Quentin F. Ingerson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, claim 3, line 26, after "I" delete "and" and substitute therefor ---to--- sips-m I Attest:

Fletcher wmum E. Amsnng Office! Gomissionor of Patents FORM PO-IO5O (IO-69) USCOMNPDC Jane-p60 LI 5 GOVIINNENY PIINT'NG OFFICE I... O-Jlllll 

